The invention relates to a windshield wiper drive mechanism, having a drive mechanism, a drive lever whose first end is connected to the drive mechanism so that it can be pivoted about a drive axis, a coupling lever whose first end is connected to the second end of the drive lever by a coupling joint with a defined rotational axis and whose second end is connected to a windshield wiper blade, and a power takeoff lever, which is connected to the coupling lever.
The drive lever, coupling lever and power takeoff lever form a four-bar mechanism, whose function is to generate a reciprocating motion to create a larger field swept by the wipers. Another function of such a four-bar mechanism can be to vary the positioning angle of the windshield wiper blade relative to the window to be cleaned in a purposeful way.
On the assumption that all the rotational axes of the four-bar mechanism are parallel to one another and moreover the windshield wiper blade is resting on a flat window that is perpendicular to the rotational axes, the resultant orientation of the plane of longitudinal symmetry of the windshield wiper blade is always perpendicular to the plane of the window. The result can be that at the turning points of the windshield wiper blade, that is, at the transition from one direction of motion to the other at the two extreme positions, the windshield wiper blade will rattle against the window, since the wiper lip of the unpositioned windshield wiper blade has to fold over out of one bent-away position to the other. This problem can become more crucial if production variations and so forth result in incorrect positions of the windshield wiper blade. In principle, the wiper lip of the windshield wiper blade folds over more easily and with less noise, the more forcefully the windshield wiper blade is positioned against the window on reaching the terminal position corresponding to the new direction of motion. To achieve this kind of advantageous positioning angle, which is also called a normal-line error, it is known to orient the rotational axes of the four-bar mechanism obliquely to the window to be cleaned. In this way, at the respective turning points of the windshield wiper blade, a small positioning angle can be achieved. A greater obliquity of the drive axis is not possible, however, because otherwise a collision would occur between the drive lever or coupling lever, on the one hand, and the vehicle window or hood, on the other.
The object of the invention is thus to refine a windshield wiper drive mechanism of the type defined at the outset such that in a purposeful way, larger positioning angles of the windshield wiper blade relative to the window in the region of the two turning points are possible.
The windshield wiper drive mechanism of the invention has the advantage that with little installation space and purely mechanically, a purposeful variation of the positioning angle of the windshield wiper blade at the respective turning points is possible. The oblique position transmitted to the coupling arm and thus to the windshield blade is obtained solely on the basis of the oblique position of the rotational axis of the coupling joint relative to the drive axis of the drive lever. The drive lever furthermore executes a pivoting motion in a single plane, thus preventing a collision with the window of the vehicle or with the hood. By means of the orientation of the rotational axis of the coupling joint in space relative to a hypothetical neutral position, which is parallel to the drive axis, the size of the positioning angle of the windshield wiper blade and the position of the windshield wiper drive mechanism at which the drive angle is maximal can be adjusted.